Gyratory crushers are used for crushing ore, mineral and rock material to smaller sizes. Typically, the crusher comprises a crushing head mounted upon an elongate main shaft. A first crushing shell is mounted on the crushing head and a second crushing shell is mounted on a frame such that the first and second crushing shells define together a crushing gap through which the material to be crushed is passed. A driving device is arranged to rotate an eccentric assembly about the lower portion of the shaft so as to cause the crushing head to perform a gyratory pendulum movement and crush the material introduced in the crushing gap. US 2009/0008489 discloses a hydraulically adjustable cone crusher in which an axial bearing assembly comprises a hydraulic adjustment cylinder for adjusting the setting of the crusher. U.S. Pat. No. 4,919,349 discloses a gyratory crusher having a dual seal arrangement that utilises forced air and a gasket arrangement to block contaminants entering the crusher. SU 897280 describes a cone crusher that has a step cup bearing to absorb and transmit the crushing force of the crusher head.
The gyratory pendulum movement of the crushing head is supported by a lower bearing assembly positioned below the crushing head and a top bearing into which an upper end of the main shaft is journalled. Typically, the main shaft upper end is protected against wear by a sleeve. Commonly, the protective sleeve comprises a cylindrical geometry and is held at the main shaft via an interference or friction fit. This arrangement however requires the sleeve to be heated to increase its diameter to enable mounting and possible disassembly at the main shaft.
Example protective sleeves are disclosed in U.S. Pat. No. 1,592,313; U.S. Pat. No. 1,748,102; RU 718160 and RU 940837.
However, a number of problems exist with conventional protective sleeves. In particular, if the time taken to friction fit the heated sleeve onto the main shaft end is too great it is not uncommon for the sleeve to cool and shrink before it is forced onto the shaft to the correct and final position. Additionally, disassembly is often problematic as the sleeve is required to be cut before it can be removed. On large crushers, protective sleeves have a substantial wall thickness and this cutting operation can be time and labour intensive with the added risk of potential damage to the shaft. What is required is a main shaft sleeve that addresses the above problem.